Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$104.72	10.353%	$115.5617	$115.56	$115.55	$115.60
Purchase #2	$100.29	9.370%	$109.6872	$109.69	$109.70	$109.70
Purchase #3	$77.61	10.523%	$85.7769	$85.78	$85.80	$85.80
Purchase #4	$241.76	13.313%	$273.9455	$273.95	$273.95	$273.90
Purchase #5	$118.72	11.418%	$132.2754	$132.28	$132.30	$132.30
Purchase #6	$29.58	5.248%	$31.1324	$31.13	$31.15	$31.10
Purchase #7	$120.29	13.486%	$136.5123	$136.51	$136.50	$136.50
7 purchase totals =	$792.97		$884.8914	$884.90	$884.95	$884.90